1. Field of the Invention
The present invention relates to bone fusion devices, and, more particularly, to bone fusion devices for fusing phalanges together.
2. Description of the Related Art
Digital deformities of the fingers and toes are some of the most common conditions encountered by orthopedists and podiatrists. Patients with digital deformities often experience significant pain from structural abnormalities. Some of these abnormalities are acquired, caused by traumatic injuries, neuromuscular pathologies, systemic diseases, or mechanical problems secondary to extrinsic pressures. The deformities are popularly known as either mallet finger, jersey finger, coach's finger, hammertoe, as well as a host of others indicative of several different pathologies.
Hammertoe deformity, the most common deformity of the lesser toes, is a flexion deformity of the proximal interphalangeal (PIP) joint of the toe, with hyperextension of the metatarsophalangeal (MTP) and distal interphalangeal (DIP) joints. Progressive PIP joint flexion deformity typically leads to compensatory hyperextension of the MTP and DIP joints. This makes the PIP joint prominent dorsally. Pain occurs due to rubbing of the prominence against the patient's shoe. The deformity is flexible at first but usually becomes fixed over time. When the deformity is flexible, various procedures can be utilized that involve manipulation of the involved tendons (such as orthotics). However, when the deformity is fixed, PIP fusion or joint replacement is often required.
In order to prevent recurrence of the deformity and ensure the success of the surgical procedure, a PIP joint arthrodesis is typically performed. The “end-to-end” or “peg-in-hole” techniques are the most commonly used procedures. The PIP joint is aligned with the rest of the toe in a corrected anatomical position and maintained in place by the use of a Kirschner wire (K-wire) of a selected diameter which is driven through the joint.
Another type of PIP joint fusion technique utilizes a fusion pin rather than a K-wire driven through the PIP joint. Referring to U.S. Pat. No. 7,041,106 (Carver et al.), which is assigned to the assignee of the present invention, an interphalangeal fusion pin may be used at a PIP joint of a human foot. The fusion pin may have an anatomically correct angle for the PIP joint (FIG. 4 of the '106 patent; e.g., 172.5°, and may be formed from a bioresorbable material.